function [pos] = optimal_fixrssn(pix,rss0,n, rss, fillvalue, pixnumber, prev,width,height)
    options = optimoptions('fmincon', 'MaxIter', 100); 
    [~, pos] = evalc('fmincon(@(t)(costfunction_fixrssn(t, rss0,n,pix, rss, fillvalue, pixnumber)), prev,[],[],[],[],[0,0],[width,height], [], options)');
end